The invention is directed to improvements in damping devices including an hydraulic shock absorber.
A damping device is already known (German Offenlegungsschrift No. 16 55 647), which is connected to a regulating device located outside a shock abosrber. By means of the regulating device, a variable control pressure is generated that acts upon a control device disposed inside the shock absorber affecting the throttle cross sections that are definitive for the damping. The side of the control device not exposed to the control pressure is acted upon by both the force of a compression spring and the pressure of one of the work chambers of the shock absorber. Parallel to the throttle cross section monitored by the control device, the two work chambers of the shock absorber are also connected to one another by further connecting conduits, which are provided with check valves. The known device permits adjustment of the shock absorber characteristic curve even during driving.
From German Offenlegungsschrift No. 27 38 455 or Great Britain Pat. No. 2 003 255, an active damping system is known which has a high-pressure pump, a high-pressure reservoir and metering valves for controlling the pressure in the work chambers. Since this is a vehicle damping system that functions only actively, all the components must be designed for very high capacity (up to 5 kW per wheel), which makes such a damping system very expensive, and uneconomical for common vehicles.
However, active dampers do have economic advantages in cases in which only little capacity is needed. This is less pertinent to high damping values than to applications of a damper in which, above all, it is the internal friction inside the vehicle/suspension/damping system that predominates. This is especially true for driving over good roads. Here a low-capacity but fast-response active damping can offer a notably more comfortable ride than is provided by purely passive damping.